In this paper, a complementary metal oxide semiconductor (CMOS) image sensor for low-power operation with a variable frame rate is presented. The operating current of the CIS can be reduced by varying the frame rate of the CMOS image sensor (CIS), thus decreasing power consumption effectively. The proposed image sensor has two modes: normal mode and lowpower mode. In the low-power mode, the operating current of the pixel array can be controlled according to the frame rate of the CIS. At lower frame rates, the operating current of the pixel array is smaller than in the normal mode. The power consumption of the proposed CIS is determined by the on and off ratios of the bias current. The proposed image sensor was fabricated and measured with a 2-poly 4-metal 0.35 μm standard CMOS process.